A third eye comes in handy—if you’re a lizard, that is. This so-called parietal eye, which is also found in some fish and amphibians, is made up of a patch of light-sensitive cells and helps guide lizards by the sun’s light, according to the results of a study published in Journal of Experimental Biology.

To test how third eyes… help them find their way, biologists at Italy’s University of Ferrara first trained Italian wall lizards to swim from the center of a small outdoor swimming pool to a hidden ledge at its edge. A fence was erected around the pool, so that the only visual point of reference was the position of the sun. The lizards passed the test.

But when researchers put some of the lizards in rooms lit out-of-sync with the sun’s rhythm, those animals were unable to find the ledge once they were moved to the outdoor pool–apparently because the sun wasn’t where the reptiles expected it to be.

The weirdest part? Apparently, we humans also possess a third eye (or something like it, anyway). Wired says:

Humans also have a version of the third eye system. Unfortunately for hikers and drivers, it’s located under our skulls. It’s essential for spatial processing, but not much help if you’re lost.